Washington (CNN) - U.S. Surgeon General Regina Benjamin announced late Wednesday that she will step down next month after four years in the post.

Benjamin, a longtime advocate for a health care model centered on wellness and preventable treatment, announced her decision in an e-mail to staff, thanking them for supporting her vision.

"My goal was to create a grassroots movement, to change our health care system from one focused on sickness and disease to a system focused on wellness and prevention. With your help, that movement has begun," Benjamin wrote.